A vulcanizing defect referred to as blister defect may occur when vulcanizing a pneumatic tire. Blister defects are defects where water and residual air that are included in the rubber, as well as the air remaining at steps formed at an end part of a tire component when forming the tire are locally collected during vulcanizing, and the resulting air bubbles are not completely dispersed during vulcanizing, and cause blisters that remain in the tire. The moisture and residual air that are included in the rubber form countless bubbles during the initial stage of vulcanization, and most of the bubbles are eliminated by microdispersion during vulcanizing. However, air bubbles collect in areas where the pressurizing force is weak during microdispersion, and bubbles may reoccur to form blisters after vulcanizing is complete.
In order to suppress blister defects, the tire component is pressed by a stitcher during tire formation to promote air dispersion, and air is discharged through vent holes provided on the inner surface of the mold during vulcanizing, but the residual air inside the tire cannot be sufficiently discharged simply by this method.
In response, and based on the finding that air pockets are easily formed between the carcass layer and members adjacent thereto, there is a proposal to provide an organic fiber cord for absorbing air that is not covered with rubber on at least one surface of the carcass layer, and the residual air between the carcass layer and the adjacent members is absorbed by this organic fiber cord, and thus the formation of air pockets during vulcanizing can be prevented (for example, refer to International Patent Application Publication No. WO 2013/035555).
However, if the organic fiber cord for absorbing air which is not rubber coated is provided on at least one surface of the carcass layer as described above, while the residual air between the carcass layer and the adjacent members can be absorbed, at the present, blister defects cannot necessarily be effectively suppressed. Furthermore, if the organic fiber cord for absorbing air that is not rubber coated is provided on the surface of the carcass layer, there is a possibility that the organic fiber cord will detach or become misaligned during the tire forming step.